通过相机捕获显示图像时图像视图出错

Question

我是 android 新手，我正在尝试让我的手机摄像头拍照并在图像视图中显示它。当图像被捕获时，它被正确保存，但之后应用程序停止工作，当图像应该显示在图像视图中时。任何帮助表示赞赏。我搜索了一些主题，但仍然没有任何效果。 代码如下：

package myfirstapp.myapps.me.camera;

import ...

public class MainActivity extends ActionBarActivity {
    ImageButton camBtn;
    ImageView imageView;
    ScrollView scrollView;

    private File imageFile;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void OpenCam(View view) {
        Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        imageFile=new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),"image.jpg");
        Uri tempURI=Uri.fromFile(imageFile);
        intent.putExtra(MediaStore.EXTRA_OUTPUT, tempURI);
        intent.putExtra(MediaStore.EXTRA_VIDEO_QUALITY, 1);

        startActivityForResult(intent, 0);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == 0)//==0 the same where startActivityForResult(intent, 0) so we are in the same process
        {


            switch (resultCode){
                case Activity.RESULT_OK:
                    if(imageFile.exists())
                    {
                        Toast.makeText(MainActivity.this, "Image was saved at "+imageFile.getAbsolutePath(), Toast.LENGTH_SHORT)
                                .show();
                        Bitmap myBitmap = BitmapFactory.decodeFile(imageFile.getAbsolutePath());

                        ImageView myImage = (ImageView) findViewById(R.id.imageView);

                        myImage.setImageBitmap(myBitmap);
                    }
                    else
                    {
                        Toast.makeText(MainActivity.this, "Image wasn't saved", Toast.LENGTH_SHORT)
                                .show();
                    }
                    break;
                case Activity.RESULT_CANCELED:
                    Toast.makeText(MainActivity.this, "Image capture was cancelled", Toast.LENGTH_SHORT)
                            .show();
                    break;
            }
        }
    }
}

堆栈跟踪

原因：java.lang.RuntimeException：传递结果失败 ResultInfo{who=null, request=0, result=-1, data=null} 到活动 {myfirstapp.myapps.me.camera/myfirstapp.myapps.me.camera.MainActivity}： java.lang.NullPointerException 在 android.app.ActivityThread.deliverResults(ActivityThread.java:3410) 在 android.app.ActivityThread.performResumeActivity(ActivityThread.java:2817) 在 android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2859)

Answer 1

请仔细阅读此代码：

    public static final int REQUEST_IMAGE_CAPTURE = 1;
    public static final int RESULT_LOAD_IMAGE = 10;
     private Bitmap myBitmap;
     ImageView myImage ;
        public void OpenCam(View view) {

              Intent takePictureIntent = new             Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                    if     (takePictureIntent.resolveActivity(getPackageManager()) != null) 
                    {

                        startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
                    }
    }

还有，

@Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) 
    {


        if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) 
        {
            Bundle extras = data.getExtras();
            myBitmap= (Bitmap) extras.get("data");

             myImage = (ImageView) findViewById(R.id.imageView);

                    myImage.setImageBitmap(myBitmap);
        }

        if (requestCode == RESULT_LOAD_IMAGE && resultCode == RESULT_OK && null != data) {
            Uri selectedImage = data.getData();
            String[] filePathColumn = { MediaStore.Images.Media.DATA };

            Cursor cursor = getContentResolver().query(selectedImage,filePathColumn, null, null, null);
            cursor.moveToFirst();

            int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
            String picturePath = cursor.getString(columnIndex);
            cursor.close();

            myBitmap= BitmapFactory.decodeFile(picturePath);

            //          photoUri = picturePath;



        myImage.setImageBitmap(myBitmap);

        }

    }

Answer 2

您为什么要先保存并尝试显示保存的图像文件。使用从onActivityResult 返回的data。在内存中实际创建文件之前，会发送广播，以便刷新目录并显示新文件。但更好的是使用相机意图返回的数据。

替换您的此代码

Bitmap myBitmap = BitmapFactory.decodeFile(imageFile.getAbsolutePath());

                        ImageView myImage = (ImageView) findViewById(R.id.imageView);

                        myImage.setImageBitmap(myBitmap);

有了这个

ImageView myImage = (ImageView) findViewById(R.id.imageView);
Bitmap photo = (Bitmap) data.getExtras().get("data"); 
                myImage.setImageBitmap(photo);

Answer 3

first : 注释该行 intent.putExtra(MediaStore.EXTRA_VIDEO_QUALITY, 1); // no need to write 用于捕获相机

第二个：使用这一行

imageFile=new File(Environment.getExternalStorageDirectory().getAbsolutePath()+"/abc); // abc folder name

而不是

imageFile=new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),"image.jpg");

注意：您的代码可以在 kitkat 上运行，但棒棒糖会崩溃，因为在棒棒糖 imageFile 返回 null 所以 Uri 无法在文件中转换。希望您的问题能够解决。在打开相机之前还有一件事，你应该检查 sdcard 权限。